bitop

include/bitop.h

@@ -2,6 +2,8 @@
 #include <limits.h>
 #include <stdint.h>
 
+#include <utility>
+
 namespace bitop {
 
 /* Return the number of bits of the data type.
@@ -338,6 +340,55 @@ template <typename T=unsigned int> static inline unsigned int log2(T v) {
     return ~0u;
 }
 
+
+/* return type, pair */
+class bitseqlengthandpos_ret_t {
+    public:
+        bitseqlengthandpos_ret_t(const unsigned int _start,const unsigned int _length) : start(_start), length(_length) { }
+    public:
+        bool operator==(const bitseqlengthandpos_ret_t &n) const {
+            return  (n.start == start) &&
+                    (n.length == length);
+        }
+        bool empty(void) const {
+            return  (start == 0u && length == 0u);
+        }
+    public:
+        unsigned int    start, length;
+};
+
+/* return a pair struct representing start and length of a series of 1 bits */
+template <typename T=unsigned int> static inline bitseqlengthandpos_ret_t bitseqlengthandpos(T v) {
+    if (v != bitop::allzero<T>()) {
+        unsigned int start=0,length=0;
+
+        /* count zeros */
+        while ((v & (T)0xFFUL) == (T)0x00UL) {
+            start += (T)8;
+            v >>= (T)8UL;
+        }
+        while (!(v & (T)1u)) {
+            start++;
+            v >>= (T)1UL;
+        }
+
+        /* count ones */
+        while ((v & (T)0xFFUL) == (T)0xFFUL) {
+            length += (T)8;
+            v >>= (T)8UL;
+        }
+        while (v & (T)1u) {
+            length++;
+            v >>= (T)1UL;
+        }
+
+        return bitseqlengthandpos_ret_t(start,length);
+    }
+
+    return bitseqlengthandpos_ret_t(0u,0u);
+}
+
+
 void self_test(void);
 
 }

src/gui/bitop.cpp

@@ -245,6 +245,44 @@ void self_test(void) {
     assert(negate<unsigned long>(1) == ~1ul);
     assert(negate<unsigned long long>(0) == ~0ull);
     assert(negate<unsigned long long>(1) == ~1ull);
+
+    assert(bitseqlengthandpos(0)   == bitseqlengthandpos_ret_t(0,0));
+    assert(bitseqlengthandpos(1)   == bitseqlengthandpos_ret_t(0,1));
+    assert(bitseqlengthandpos(3)   == bitseqlengthandpos_ret_t(0,2));
+    assert(bitseqlengthandpos(7)   == bitseqlengthandpos_ret_t(0,3));
+    assert(bitseqlengthandpos(15)  == bitseqlengthandpos_ret_t(0,4));
+    assert(bitseqlengthandpos(31)  == bitseqlengthandpos_ret_t(0,5));
+    assert(bitseqlengthandpos(63)  == bitseqlengthandpos_ret_t(0,6));
+    assert(bitseqlengthandpos(127) == bitseqlengthandpos_ret_t(0,7));
+    assert(bitseqlengthandpos(255) == bitseqlengthandpos_ret_t(0,8));
+
+    assert(bitseqlengthandpos(1)   == bitseqlengthandpos_ret_t(0,1));
+    assert(bitseqlengthandpos(2)   == bitseqlengthandpos_ret_t(1,1));
+    assert(bitseqlengthandpos(4)   == bitseqlengthandpos_ret_t(2,1));
+    assert(bitseqlengthandpos(8)   == bitseqlengthandpos_ret_t(3,1));
+    assert(bitseqlengthandpos(16)  == bitseqlengthandpos_ret_t(4,1));
+    assert(bitseqlengthandpos(32)  == bitseqlengthandpos_ret_t(5,1));
+    assert(bitseqlengthandpos(64)  == bitseqlengthandpos_ret_t(6,1));
+    assert(bitseqlengthandpos(128) == bitseqlengthandpos_ret_t(7,1));
+    assert(bitseqlengthandpos(256) == bitseqlengthandpos_ret_t(8,1));
+
+    assert(bitseqlengthandpos(2)   == bitseqlengthandpos_ret_t(1,1));
+    assert(bitseqlengthandpos(6)   == bitseqlengthandpos_ret_t(1,2));
+    assert(bitseqlengthandpos(14)  == bitseqlengthandpos_ret_t(1,3));
+    assert(bitseqlengthandpos(30)  == bitseqlengthandpos_ret_t(1,4));
+    assert(bitseqlengthandpos(62)  == bitseqlengthandpos_ret_t(1,5));
+    assert(bitseqlengthandpos(126) == bitseqlengthandpos_ret_t(1,6));
+    assert(bitseqlengthandpos(254) == bitseqlengthandpos_ret_t(1,7));
+    assert(bitseqlengthandpos(510) == bitseqlengthandpos_ret_t(1,8));
+
+    assert(bitseqlengthandpos(4)   == bitseqlengthandpos_ret_t(2,1));
+    assert(bitseqlengthandpos(12)  == bitseqlengthandpos_ret_t(2,2));
+    assert(bitseqlengthandpos(28)  == bitseqlengthandpos_ret_t(2,3));
+    assert(bitseqlengthandpos(60)  == bitseqlengthandpos_ret_t(2,4));
+    assert(bitseqlengthandpos(124) == bitseqlengthandpos_ret_t(2,5));
+    assert(bitseqlengthandpos(252) == bitseqlengthandpos_ret_t(2,6));
+    assert(bitseqlengthandpos(508) == bitseqlengthandpos_ret_t(2,7));
+    assert(bitseqlengthandpos(1020)== bitseqlengthandpos_ret_t(2,8));
 }
 
 }